| Co-Investigator(Kenkyū-buntansha) |
AKO Junya University of Tokyo, Hospital Intemal Medicine Assistant, 医学部・附属病院, 技官 (60292744)
ETO Masato University of Tokyo, Hospital Intemal Medicine Assistant Prof., 医学部・附属病院, 助手 (80282630)
KOZAKI Koichi University of Tokyo, Hospital Intemal Medicine Assistant Prof., 医学部・附属病院, 助手 (80272540)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1998: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1997: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
1. The regulation of vascular smooth muscle cell (VSMC) proliferation is important to prevent vascular diseases. We report that cell density plays a crucial role in the effect of antioxidant treatment on VSMC. Pyrrolidinedithiocarbamate (PDTC) treatment caused apoptosis in rat aortic smooth muscle cells (RASMC) at low cell density (1x104/cm2). PDTC treatment resulted in cell cycle arrest in RASMC at high cell density (5x104/cm2). This cell cycle arrest was reversible by the removal of PDTC. A cyclin-dependent kinase inhibitor, p21WAF1/CIP1, was induced in high density RASMC by PDTC. treatment. These results indicate that antioxidant treatment causes either cell cycle arrest or apoptosis in different culture conditions. This in vitro phenomenon may provide new information about the control of SMC growth in vivo.
2. Red wine polyphenols have been shown to contribute to the "French paradox" phenomenon consisting of lower morbidity and mortality from coronary heart disease in the French pop
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ulation. Although vascular smooth muscle cell (VSMC) proliferation plays an important role in the progression of atherosclerotic lesions, the effects of red wine polyphenols on VSMC proliferation have not been elucidated. We extracted the total polyphenolic fraction, named RW-PF, from red wine using column chromatography. Treatment with RW-PF showed a potent inhibitory effect on the proliferation and DNA synthesis of cultured rat aortic smooth muscle cells (RASMC). In contrast, the inhibitory effect of RW-PF on the proliferation of bovine carotid endothelial cells was only observed at much higher concentrations. To elucidate the molecular mechanisms of this antiproliferative effect of RW-PF on RASMC, we investigated the effects of RW-PF on cell cycle regulation. RW-PF downregulated the expression of cyclin A mRNA and cyclin A promoter activity. In addition, RW-PF decreased the binding of nuclear proteins to the activating transcription factor (ATF) site in the cyclin A promoter, and downregulated the mRNA levels of transcription factors, cyclic AMP-responsive element-binding protein (CREB) and ATF-1. These results suggest that the downregulation of cyclin A gene expression may contribute to the antiproliferative effect of red wine polyphenols on RASMC through the inhibition of transcription factor expression.
3. Peroxisome proliferator-activated receptor gamma (PPARgamma), a member of nuclear receptors, is expressed at a high level in adipose tissue and plays an important role in adipocyte differentiation. In the present study, we identified the expression of PPARgamma in rat aortic smooth muscle cells (RASMC) using reverse transcription-polymerase chain reaction and gel mobility shift assay. In addition, to investigate whether PPARgamma in RASMC is functional or not, we examined the effect of two specific ligands for PPARgamma, a thiazolidinedione anti-diabetic agent, troglitazone, and 15-deoxy-Delta12, 14-prostaglandin J2, on the transcriptional activity of PPAR responsive element (PPRE). A significant increase in the activity of PPRE by addition of these ligands was found. These results suggest that in RASMC, target genes for PPARgamma may be activated by specific ligands for PPARgamma through PPRE in their promoters. In conclusion, PPARgamma is expressed and functional in vascular smooth muscle cells. Less
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